Synthetic plastics account for the use of 7% of fossil fuels in the world. The limited resources and rising price of fossil fuels present a challenge to seek developing renewable resources for manufacturing of “green” plastics. However, applications of renewable polymers lag significantly behind petrochemical-derived polymers, partially because of limitations in the monomer resources and the derived polymers with controlled properties.
As such, synthesis of renewable compounds and polymer-based materials from natural resources has attracted significant attentions, as these compounds and materials have the promise to replace compounds and plastics derived from petroleum chemicals. Cationic compounds have many applications such as antimicrobials, biocides, antibiotics, drug, surfactants, etc. Cationic polymers have many applications such as antimicrobial materials, antifouling coatings, packaging materials, surfactants, for use in water sanitation and purification, and in drug delivery, etc.
Produced in quantities of more than one million tons annually, rosin (including gum rosin, wood rosin and tall rosin), whose major components are resin acids (or rosin acids) including abietic acid, levopimaric acid, hydroabietic acid, dehydroabietic acid, pimaric acid, is generally used as ingredients for inks, vanishes, adhesives, cosmetics, medicines, chewing gums, etc. Rosin acids have three characteristic functionalities: hydrophenanthrene rings, carboxylic acid, and conjugated dienes.
Rosin has been used as raw materials to prepare cationic compounds. For example, rosin has been widely used as raw materials to prepare polymeric materials, in which rosin moieties are placed either at the backbone or at the side groups. Radical polymerization has been used to prepare vinyl polymers, while condensation polymerization has produced many polymers. (See e.g., U.S. Patent Publication No. 2011/0086979 of Chuanbing Tang titled “Polymers Derived from Rosin and Their Methods of Preparation”).
However, the cationic group is, in these methods, attached to the rosin moiety through the carboxylic acid group. Thus, the most readily functionalizable group of the rosin moiety (i.e., the carboxylic acid group) is no longer available for further reaction according to these methods. Such limited functionality hinders the usefulness of the polymers formed according to these methods.
As such, a need exists for methods of preparing cationic compounds and cationic polymers from rosin (e.g., resin acids) without utilizing the carboxylic acid group of the rosin moiety.